Focal Length and Lens

Lens• Camera lens is assembly of optical pieces(mirrors and lenses) used in conjunction witha camera body and mechanism to makeimages of objects either on photographic filmor image sensors.

Classification of lens• Differences in aperture.• Differences in focal length (Prime and Zoom).• Fixed or interchangeable.• Differences in lens mount. 

Focal Length• It is the calculation of optical distance fromthe point where light rays converge (opticalcenter) to form a sharp image of an object tothe sensor or film.

Angle of view• The angle of view is the amount of a scene that a lens can take in, measured in degrees.

• Fish Eye lens gives 180 degree• Telephoto gives 12 degree

Prime and Zoom Lens• Prime Lens: The lens with fixed focal length (18mm, 50mm, 80 mm, 300mm). Prime lens provide wider aperture and image quality. 

• Zoom lens: The lens with variable focal length (18 mm – 55mm, 10 mm – 18 mm, 70 mm –300mm). Aperture is depended upon the focal length. 

Lens Mount• It is a mechanical and electrical interfacebetween a photographic camera body and alens.

• Canon EF Mount (Electro‐Focus)• Canon EF‐S (Small Image Circle)• Nikon F Mount (‘F’ stands for Reflex)

Image Sensor• Full Frame: camera with a sensor the samesize as a 35mm film negative, measuring 36 x24mm.

• Cropped Sensor: APS‐C (Advanced PhotoSystem type‐C) approximately equivalent insize to the Advanced Photo System "classic"negatives of 25.1 × 16.7 mm